Starrett 98-12 Precision Machinists' Level, 12" (300mm) Length, With Ground Single And Cross Test Vials 12" precision machinists' spirit level with a main vial and a cross-test vial for determining horizontal plane and a plumb vial for determining vertical plane Graduated, ground glass main vial has a sensitivity of 0.42 mm/m or 80 to 90 seconds and is adjustable to a positive setting for accurate results Cross-test vial enables simultaneous leveling in two directions V-shaped groove along the base provides reliable seating when leveling round items Cast iron base for durability